Many types of input devices are available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens, and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens generally allow a user to perform various functions by touching (e.g., physical contact or near-field proximity) the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can generate touch images. A controller can interpret the touch images in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch image.
To reduce the thickness and/or manufacturing costs of the touch sensor panel, some or all of the touch sensors can be disposed on the cover material and/or the opaque mask, thereby avoiding a separate substrate. The cover material can include an opaque mask (e.g., black mask) formed along one or more portions of the cover material to conceal bond pads (for off-panel connections) and/or traces used to route signals from touch electrodes to the bond pads. In some instances, the opaque mask can include one or more materials that outgas during manufacture due to, e.g., high temperature deposition processes. The outgas sing can cause the conductive material that forms at least a portion of the routing traces, bond pads, and/or touch sensors located in the border area to have a larger resistance. The larger resistance can make the routing traces, bond pads, and/or touch sensors susceptible to certain events such as arcing and discharge/joule heating. Accordingly, touch sensor configurations for reducing electrostatic discharge (ESD) events in the border area of the touch sensor panel may be desired.